1. Field of the Invention
The invention is directed to a draw-in device for feeding a plurality of webs of printing stock, preferably paper into a printing machine, and to a process for feeding webs.
2. Description of the Prior Art
A draw-in device in which only one web of printing stock at a time is fed via different feed paths is known from DE 22 41 127 C3. A paper web to be printed can be guided by means of this draw-in device via preadjusted points or switches through the individual printing units of a printing machine in a desired manner, the fed web being attached to a finite, drivable draw-in element.
There are also printing machines in which a plurality of printing stock webs must be printed simultaneously. For this purpose, the material webs are fed in one after another and the entire printing machine runs during the feeding process. Although this process for feeding webs of material saves much time compared with a manual feed, there is a high percentage of waste which occurs, for example, in a printing machine with four adjacent printing unit towers when the fourth material web is drawn into the printing machine after the other three material webs have already been drawn in and must now move along with this fourth material web.
If one attempted to feed in all material webs at the same time in an effort to save time and economize on wasted printing stock, the material webs would arrive at their destinations at different times due to the varying lengths of the feed paths and the different amounts of time accordingly required to travel the feed paths. The first draw-in element to arrive at its destination would cause the entire printing machine to stop. The draw elements, such as cylinders or draw rollers, coming into contact with this material web would then have to be decoupled and the printing machine would then have to be restarted and the rest of the material webs would continue to be fed through until the next shortest material web arrived at its destination and the draw elements associated with this path would be decoupled in a corresponding manner.
Even if it were possible for draw elements associated with one path to be decoupled individually while the draw elements associated with other paths continued to rotate, it would still not be possible to recouple stationary and running paths at the conclusion of the feed process in a search run required for a definite correspondence coupling.
Consequently, it is necessary to consecutively draw in the webs. Accordingly, when the second web is drawn in, the first web moves along with it and when the third web is drawn in the first and second webs move along with it. For example, if the distance covered by a web of printing stock between a reel changer and a cutting mechanism in a printing machine is 35 meters and four webs of printing stock are to be ted one after the other, there is a net feed waste of 350 meters. The time required for the feed of four webs is four times that required for one web of printing stock.